XML : There isn't antlib.xml in my ant-contrib-0.3

I am trying to use task for. I tried with this task definition:

      <taskdef resource="net/sf/antcontrib/antlib.xml">          <classpath>              <pathelement location="${infrastructure-base-dir}/apache-ant-1.9.6/lib/ant-contrib-0.3.jar"/>          </classpath>      </taskdef>    

But didn't work. This message appear:

Problem: failed to create task or type for

So I decider to unzip ant-contrib-0.3.jar to see what's inside. And there wasn't antlib.xml in this path: net/sf/antcontrib/. So what would you advise me in order to make task FOR to work?